Based on the importance of the avian model for delineating cell- mediated and humoral immune responses, the broad objectives of this study are to obtain basic information on the humoral immune response of chickens. These studies will emphasize the genetics of the immune response in the following: (1) the elucidation of the specific immune response (Ir) genes and the identity of the cell type where Ir genes are expressed; (2) the temporal dependence of antibody affinity; (3) the search for homogeneous IgG and IgM antibodies. A search for Ir genes will be made in several isogenic lines and randomly-bred chickens. Bovine serum albumin and antigens of limited complexity will be used. Previously, we have found that the chicken responds to intravenous injection of aqueous DNP-protein by synthesizing both IgM and IgG antibodies for long periods of time; the IgM antibody also occurs in secondary and tertiary responses. Thus, we propose to reevaluate the roles of various parameters (dose of immunogen, adjuvant vs. no adjuvant, hapten/protein ratios of immunogen, etc.) on the binding affinities of anti-DNP IgG and IgM antibodies obtained from the same sera from individual chickens. The reevaluation is done without the complicating factors of adjuvant. Binding constants will be determined by equilibrium dialysis, fluorescence quenching and the Farr method. Homogeneous IgG and IgM antibodies will be isolated and made available for structural studies. A homogeneous anti-DNP IgM antibody will be analyzed for the problem of valency. Three other avian species, namely, pheasants, quail and turkeys will be studied for similarities and differences from the chicken in respect to: (a) the sequential synthesis of immunoglobulin class; (b) the structure of their immunoglobulins.